Your assesment is flawless.
Unfortunately, when a thread like this one is started, it is too late for the preventative measures, and it is time for curative measures, in other words, the person already has the symptoms of the disease and are trying to save their plants.
People, in general, don't research plant diseases before they plant. They look for help after they see symptoms of disease. Kinda like going to a doctor, you know something is wrong, but you don't try to diagnose yourself. When the doctor identifies the problem and saves the patient, he then tells them about the preventative measures they should take to avoid future contamination.
But, your assesment still is flawless, you got it all correct.